Analog Angle Article

Digital isolator IC relieves USB data lines of intimate physical-connection risks

Norwood, Mass —We all know the USB port: it's fast, small, well supported, inexpensive, and ubiquitous (have you even seen a serial port lately on a PC?). But it has one glaring problem, which becomes especially apparent and even dangerous as PC-based devices migrate into industrial and medical instrumentation applications: it is not isolated, so system faults can damage the peripheral or, conversely, endanger the operator or patient.

The solution to this problem is well known but thus far has been difficult to implement: for USB, namely, to galvanically isolate the two ends of the link from each other. This means there is no ohmic path across the connection, yet data flows as if there is a connection.

To overcome this challenge, Analog Devices has introduced what they say is the first USB data-line isolator, significantly reducing the effort and BOM needed for a discrete design alternative. Their ADuM4160 features 5 kVrms isolation (IEC 60601-1 Medical Safety and VDE 0884-10 Approvals are pending), upstream short-circuit protection, and supports 1.5 and 12 Mbps data rates (USB 1.0 and USB 2.0 compliant). Based on their established iCoupler magnetic coupling technology, which uses both CMOS and micro-transformer technologies, it combines both transmit and receive channels in the same package.

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The device operates from the 5 V USB supply or an external 3.3 V supply (via its internal regulator) and provides isolation for the D+/D- signals. The vendor maintains that this isolating technology is both more suitable and more reliable for this application than alternatives such as photodiodes and optocouplers, and uses less power (2.1 mA maximum at 1.5 Mbps; 8.4 mA at 12 Mbps, and 2.5 mA upstream idle current).

Other key specifications also include 105°C operation and >25 kV/μsec common-mode transient immunity—Bill Schweber

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Packaging and availability : The ADuM4160 is housed in a 16-lead SOIC package and is $4.89 in 1000-piece orders. Samples are available now, full production begins in June.

For more information : Analog Devices, Inc,

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